This invention relates to devices providing a lining for a valve guide to receive the stem of a reciprocating-type poppet valve in an internal combustion engine and, more particularly, to an insert particularly adapted to line or reline a worn valve guide to return it to its original or better operating condition.
Inserts for lining or relining worn valve guides in internal combustion engines are well known. Typically, the worn valve guide of an internal combustion engine is bored out to receive a cast iron insert having an inside diameter which receives the stem of a valve fitted therethrough. The cast iron sleeve is force fitted into or otherwise retained in the bored-out valve guide passageway.
Cast iron inserts of this type suffer from two major disadvantages. They are relatively expensive to manufacture, the meeting of tolerances with respect to wall thickness and concentricity requiring generally repeat machining of either the inner or outer insert surfaces following initial machining of the insert. The wear characteristics of these cast iron inserts, most importantly, leave much to be desired. They do offer the advantages, however, of having good heat transfer characteristics and have for years been produced in standard O.D. sizes minimizing the number of specialized tools required for installation.
Materials possessing wear characteristics substantially better than cast iron have been known for a substantial period of time. In this inventor's prior patents numbered 3,828,415 and 3,828,756 there is disclosed an insert fabricated from spring-tempered phosphor bronze and a method of installing the same. This insert has achieved substantial commercial success and affords, when installed, wear characteristics markedly better than those attained with cast iron. There has been a significant problem, however, with the installation of these inserts. The physical characteristics of the insert material, its mode of installation and the rather high cost of the material, more particularly, have dictated that its wall thickness be kept as thin as practical. These dictates have resulted, for any given valve stem O.D., in a liner having an installed O.D. requiring a peculiarly sized reamer or other boring tool to form the passageway within which the insert is to be installed. These reamers are very expensive and, in many cases, mechanics, repairmen and the like have chosen to continue installing the clearly inferior cast iron guides in order to avoid the time and expense involved in the purchase and selection of these peculiarly sized tools.
Similar problems are encountered where an engine has been previously rebuilt using standard size toolings. Removal of the now-worn replacement guide, as will be readily appreciated, leaves little choice but to rebuild with a cast iron or other guide having the same O.D.
The present invention provides an insert and method of fabricating the same which retains the salient features of the insert described and claimed in the aforenoted patents. At the same time, however, the invention preserves all significant advantages inherent in the prior art cast iron and similar inserts, particularly with respect to avoiding totally the necessity for peculiarly specialized tooling at the installation situs.